The present invention relates to a noncontact communication semiconductor device comprising a radio communication antenna for handling comparatively weak signals, in which power is received from a reader-writer and signals are supplied to and received from the reader-writer by radio.
Conventionally, a semiconductor device comprising an IC chip mounted on a substrate formed in the shape of card, tag or coin is known. This type of semiconductor device has a wealth of information amount and a high security performance, and therefore has come to be widely used in various fields including traffic, distribution and data communication.
Especially, a recently-developed noncontact communication semiconductor device, in which the supply of power from a reader-writer to an IC chip and the transmission/reception of signals between a reader-writer and an IC chip are performed in a noncontact fashion using a radio-communication antenna without providing any external terminal on the substrate, has the features that it is basically free of breakage of the external terminal unlike the contact, easy to store or otherwise handle, and has a long service life and the maintenance of the reader-writer is easy. Another feature is that the data cannot be easily altered for an improved security performance, and therefore future extension of the use thereof is expected in wider areas of application.
In the conventional noncontact communication semiconductor device, an IC chip with a flat circuit-forming surface, i.e. an IC chip in a thin tabular form of silicon wafer with one side thereof is formed of a required circuit pattern including arithmetic elements and storage elements. Also, a flat coil comprised of a winding coil of a conductor or a flat coil with a conductor film etched has been used as an antenna for radio communication. These antennas are generally mounted on a substrate. In recent years, however, a flat coil directly formed as a pattern on an IC chip or a coil wound around an IC chip as a core has been proposed.
A thin tabular IC chip with a required circuit pattern integrated on one side of a silicon wafer has a small bending strength. Therefore, a device with an antenna mounted on an IC chip, to say nothing of a device with an antenna mounted on a substrate, cannot be used by itself as a noncontact communication semiconductor device, but an IC chip is required to be mounted on a substrate. Thus the conventional noncontact communication semiconductor device has the disadvantage that the structure is complicated for an increased cost and the superficial shape becomes bulky.
Also, the conventional noncontact communication semiconductor device, in which the substrate is formed in the shape of card, tag or coin and the antenna mounted on the device has a directivity between the front and back sides of the substrate, naturally has a limited field of application. For example, the conventional noncontact communication semiconductor device cannot be placed and used in a fluid for measuring the flow rate and flow velocity.
The present invention has been developed to obviate this problem of the prior art, and the object of the invention is to provide a noncontact communication semiconductor device which can be produced in small size at low cost and is applicable to fields to which the application has thus far been difficult.
In order to solve the aforementioned problem, the present invention uses an IC having a three-dimensional circuit-forming surface and is so configured that an antenna for radio communication is formed as a three-dimensional pattern on the surface of the particular IC or an antenna for radio communication electrically connected to the input/output terminal of a circuit three-dimensionally formed on the circuit-forming surface is attached to the outer peripheral portion of the IC having the three-dimensional circuit-forming surface.
The aforementioned IC having a three-dimensional circuit-forming surface, unlike the IC produced by the wafer process, is fabricated in such a manner that required elements and wiring are formed using the process technique on the surface of a silicon base generated by a special method. Such an IC, in which the contour is configured with at least two flat surfaces, is of two types. One has a contour containing at least two surfaces on which the circuits are formed. The other has a contour formed as a curved surface in the shape of sphere, grain, dish, hemoglobin, tetrapod, elongate or flat ellipsoid of revolution, tetrahedron enclosure, cubic, donuts, rice grain, gourd, seal or barrel, on which curved surface the circuits are formed.
In the noncontact communication semiconductor device described above, an insulating layer may be formed as required between the IC and the antenna, and by adjusting the thickness of the insulating layer, the size, i.e. the frequency characteristic of the antenna formed on the surface of the insulating layer can be adjusted.
Of the two types of semiconductor devices described above, the semiconductor device with a radio communication antenna attached to the outer peripheral portion of the IC having a three-dimensional circuit-forming surface may be such that the particular antenna is configured with either two conductive hollow hemispheric members with the peripheral edge portions thereof arranged in opposed relation to each other through a predetermined slit, or a conductive hollow spherical member having a slit in a portion thereof. These antennas have a superior high-frequency characteristic and therefore can secure a long communication distance in spite of their small size. Also, in the case where the required communication distance is short, an antenna formed of a winding coil can be used.
In the case where the antenna described above is a winding coil or a pattern formed by the microprocessing technique such as the laser beam machining or etching on the IC surface, an arbitrary antenna pattern including the loop or dipole or a combination of the two can be used. Also, the antenna pattern is desirably multidirectional or omnidirectional, and formed to have a high sensitivity at least in three or more specific directions.
An IC having a three-dimensional circuit-forming surface such as a spherical IC has a much higher bending strength (breaking strength) than a tabular IC chip. In the case where a radio communication antenna is formed as a pattern on the surface of such an IC or a radio communication antenna is attached to the outer peripheral portion of the IC, the substrate on which the antenna is to be mounted is not required. As compared with the conventional noncontact communication semiconductor device requiring the substrate as an essential component part, therefore, the superficial shape thereof can be reduced in size remarkably, while at the same time making it possible to form a multidirectional or omnidirectional antenna having a high sensitivity in three or more specific directions. Thus, a noncontact communication semiconductor device can be configured with only an IC and an antenna. This semiconductor device, being compact and in the shape of grain, can be placed and used in a fluid, for example, for measuring the flow rate and the flow velocity. The application field of the noncontact communication semiconductor device of this type can thus be extended. Further, in view of the fact that the desired noncontact communication semiconductor device can be produced simply by forming a radio communication antenna as a pattern on the surface of the IC or by attaching a radio communication antenna to the outer peripheral portion of the IC, a noncontact communication semiconductor device can be produced at lower cost than the noncontact communication semiconductor device having a substrate.